Bile is a liquid produced by the liver that flows into the duodenum via the bile duct, hepatic ducts, gallbladder, and common bile duct. In the duodenum, bile activates digestive enzymes in pancreatic fluid and together with the pancreatic fluid breaks down fats and proteins so that they can be readily absorbed by the intestines. Because fatty acids that cannot be broken down by fats are not readily absorbed, bile acts to convert these fatty acids into an easy-to-absorb form.
The flow of bile slows down when a biliary obstruction occurs, but the liver continues to produce bile even when the flow of bile slows down. When the amount of bile produced by the liver exceeds the amount of bile flowing into the duodenum, bile is stored in the gallbladder. However, when the gallbladder becomes full, some of the bile produced by the liver accumulates in the liver. When bile flows into the duodenum, it performs the function described above. However, when bile accumulates in the liver, tissue is destroyed. This can even cause cirrhosis of the liver. Therefore, when a biliary obstruction happens, pressure relief (drainage) has to occur in the biliary tract to improve the flow of bile.
One method of draining the biliary tract is to place a tube in the biliary tract using an endoscope to form a flow path for the bile. In this method, there is an external drainage technique in which one end of a long drainage tube (external drainage tube) is placed in the biliary tract and the other end is drawn from the body via the nose to discharge bile extracorporally [see FIG. 4 (A)], and an internal drainage technique in which a short tube (internal drainage tube) is placed in the body to connect the bile duct to the duodenum and allow bile to flow intracorporeally (that is, into the duodenum) [see FIG. 4 (B)].
The external drainage technique is advantageous from the standpoint of observing the drainage effect because bile discharge conditions and discharge amounts can be grasped. However, in the external drainage technique, the external drainage tube passes through the nose, and the container used to collect the discharged bile has to be carried around all the time. This makes the patient uncomfortable. Therefore, a switch is made from the external drainage tube to an internal drainage tube once it has been determined that the purposes of the drainage have been adequately achieved.
When the switch is made from the external drainage tube to an internal drainage tube, a procedure is performed in which the external drainage tube is removed, an endoscope is inserted, and an internal drainage tube is installed. Insertion of an endoscope is somewhat painful to the patient, so it has to be performed as quickly as possible.
Various devices have been disclosed for placement of an internal drainage tube (see, for example, Patent Document 1 and Patent Document 2), and a medical device for performing this procedure quickly has been realized in the ‘Rapid Exchange Biliary Stent System’ from Boston Scientific Japan.